import type { AgentEndEvent, ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { sendNotification } from "../send.ts";
import type { Toggle } from "../config.ts";

interface AgentOutcome {
  stopReason: string;
}

function isAssistantMessage(value: unknown): value is { role: "assistant"; stopReason?: unknown } {
  return typeof value === "object" && value !== null && (value as { role?: unknown }).role === "assistant";
}

export interface AgentLoopOptions {
  completion: Toggle;
  error: Toggle;
  getSessionName?: () => string | undefined;
  notify?: (message: unknown) => void;
}

export interface AgentLoopHandlers {
  onAgentEnd: (event: AgentEndEvent, context: ExtensionContext) => void;
  onAgentSettled: (_event: unknown, context: ExtensionContext) => void;
}

/** Capture intermediate results and emit only once at the final settlement. */
export function createAgentLoopHandlers(options: AgentLoopOptions): AgentLoopHandlers {
  let latest: AgentOutcome | undefined;
  const deliver = options.notify ?? sendNotification;
  const title = (): string => {
    try {
      return options.getSessionName?.()?.trim() || "pi";
    } catch {
      return "pi";
    }
  };

  return {
    onAgentEnd(event) {
      try {
        latest = undefined;
        for (let index = event.messages.length - 1; index >= 0; index--) {
          const message = event.messages[index];
          if (isAssistantMessage(message) && typeof message.stopReason === "string") {
            latest = { stopReason: message.stopReason };
            break;
          }
        }
      } catch {
        // A malformed lifecycle event must not affect the agent loop.
      }
    },
    onAgentSettled(_event, context) {
      try {
        const outcome = latest;
        latest = undefined;
        if (context.mode !== "tui" || !outcome) return;
        if (outcome.stopReason === "aborted") return;
        if (outcome.stopReason === "error") {
          if (options.error === "on") deliver({ title: title(), body: "Stopped with error", type: "error", urgency: "critical" });
          return;
        }
        if (options.completion === "on") deliver({ title: title(), body: "Complete", type: "completion" });
      } catch {
        latest = undefined;
      }
    },
  };
}

export function registerAgentLoopHandlers(pi: ExtensionAPI, options: AgentLoopOptions): AgentLoopHandlers {
  const handlers = createAgentLoopHandlers(options);
  pi.on("agent_end", handlers.onAgentEnd);
  pi.on("agent_settled", handlers.onAgentSettled);
  return handlers;
}